Air traffic control improvements are key to cutting aviation emissions in the short term, finds new Oxford study

(graphic: Boeing)

Wed 10 Feb 2010 – Biofuels could reduce pollution and better technology boost efficiency but neither will have the global impact that improved flight management could achieve, says a new report by the Smith School of Enterprise and the Environment at the University of Oxford. Dr Chris Carey, the Smith School’s aviation expert, says the most obvious target for improving efficiency in aviation is engines – the source of emissions – but major technological innovations are a massive financial risk and new, more efficient aircraft are slow to reach the market. However, in a best-case scenario, which foresees major advances in aircraft technology, a high take-up in jet biofuels and a fully integrated global air traffic management system, aviation emissions could be cut by up to 95 percent by 2050.

In the short term, in five years time, if historical improvements in aerodynamics and engine and operational efficiencies continue, along with a small contribution from biofuels, then a 28% reduction in CO2 emissions could be achieved from today’s current crop of aircraft. However, delays in the uptake of new technology due to the longevity of aircraft suggest the ‘low hanging fruit’ in aviation may be changes in policy, particularly improvements in air traffic control.

“If you reduced the time aircraft spent waiting to land and taxi, allowed planes to use more direct flight paths and approach routes, and introduced a common air traffic control system, you could cut emissions from aviation by a significant amount,” says Dr Carey.

“The inaccuracy of current control systems means planes must be given a wide berth to avoid collisions. If that was improved, landing and take offs could be quicker, stacking would be reduced and planes could fly closer together by taking advantage of prevailing winds, just as Concorde did.”

The technology for both NextGen in the US and the Single European Sky will need to be retrofittable, says the study, which will allow fleet-wide roll-out much sooner than any significant technological change in propulsion or airframe architecture. Also a requirement for such technology to be utilized in any commercial aircraft flying within European or US airspace would force the majority of the world commercial fleet to fit such technology. However, notes the study, these changes are neither straightforward nor cheap but do offer a significant step change in aviation technology.

“They should be implemented as soon as possible if we are serious about cutting aviation emissions,” says Dr Carey.

In the case of long-term developments in aircraft design, not only are there technical issues but also consumer challenges to overcome. The most promising aviation technology of the future is the blended wing body aircraft, believes the study, which would likely have to be windowless and therefore may have significant problems with passenger acceptance.

Assuming that in 40 years time a best-case scenario has occurred, then a blended wing body aircraft (with a possible 32% reduction in fuel burn) carrying 800+ passengers using distributed propulsion (a further 8-10% increase in propulsive efficiency), active boundary layer control (up to 70% reduction in skin friction drag), 100% biofuel (a possible 85% reduction in CO2 emissions) and a fully integrated global air traffic management system (13% increase in efficiency) would produce an aircraft producing minimal levels of CO2 emissions – between 60% and 95% reduction in current technology – mainly from the use of biofuel.

However, concludes the study, the likelihood of the best case scenario occurring is slim, resulting from the demand from road transportation for biofuels, the various challenges faced by the technologies, as well as the financial risk of developing new aircraft and overcoming consumer perceptions.

The aviation study is part of the Smith School’s ‘Future of Mobility Roadmap’ report, an assessment of the potential for low-carbon air, land and sea.